Or this lemon curd recipe - I got it from the paper, it takes loads of patience but is delicious.
2 large or 3 smaller lemons, zest and juice
4 medium/large egg yolks
90g caster sugar
40g butter, cubed
Place the zest, lemon juice, yolks, sugar and butter together in a large heatproof bowl. Suspend the bowl over pan of simmering water, making sure that the base of the bowl does not touch the water.
Now: be patient. Linger over the curd with a wooden spoon, stirring continuously. The butter will melt and the sugar will dissolve, and over the course of the next 10-15 minutes the mixture will gradually heat up and thicken. Keep stirring over the heat until the curd is viscous enough to coat the back of the spoon – a yellow layer of curd that will hold the track left by a finger swiped through it, not a thin, translucent layer of the stuff. It'll thicken as it cools.
Take off the heat, decant into a very clean jam jar (preferably sterilised, if you're planning on storing the curd for any great length of time) and lid it. Let it cool to room temperature, then store in the fridge.